Additive manufacturing is a rapidly growing technology that is used to create reasonably accurate three-dimensional objects quickly. Current additive manufacturing techniques, such as fused-filament fabrication (FFF), are typically accomplished by forcing a polymer filament through a heated nozzle in an extrusion printhead, where the plastic feedstock is liquefied before or as it passes through the nozzle, and the feed pressure causes the material to be extruded through an exit orifice in the nozzle to form the three-dimensional object.
Existing FFF systems typically use a single extrusion printhead that extrudes a single filament of thermoplastic material. In order to change the material type or color to be deposited, the FFF process must be paused while a different filament is loaded and heated in the extrusion head. This may create termination points in the deposited material that can lead to stress concentrations, or may allow for cold flow lines that decrease the structural capability of the object being fabricated.
While current FFF deposition systems may control the feed rate and temperature of the filament material as it passes through the extrusion printhead, such FFF deposition systems lack the ability to mix multiple feedstock materials in a single extrusion head while simultaneously monitoring and controlling the viscosity and/or other rheological properties of the blended material contained in the extrusion head.